Means for correcting hectographic master sheets



United States MEANS FOR CORRECTING HECTOGRAPHIC MASTER SHEETS No Drawing. Application January 19, 1955 Serial No. 482,893

3 Claims. (Cl. 12036) My present invention relates generally to the art of hectographic printing, and has particular reference to the making of corrections on hectographic master sheets.

The principal object of the invention is the provision of a device for correcting such master sheets simply, economically, and without producing the messy scrapings which are characteristic of devices and methods hitherto employed.

In the spirit or hectographic duplicating process, a transfer sheet is used consisting of a base such as tissue paper, carrying a waxy ink coating containing spiritsoluble dye. Because such an ink coating smudges easily, and the dye discolors everything it touches, the coating is usually covered with a protective wax or other film. (A particularly desirable form of protective film, utilizing the leafing tendencies of bronze powder, is described and claimed in my Patent No. 2,671,734, issued March 9, 1954.) The desired design is transferred, by pressure from a typewriter, pencil or the like, to the under side of a master sheet, which may be of paper, plastic, aluminum foil, or the like. The preferred masters are made of clay-coated paper. When the master is completed, it carries on its under surface the design in mirror image, with the dye-carrying waxy ink coating exposed. The thin protective film of the original transfer sheet is very thin, and is largely absorbed into the clay coated surface of the master.

When errors are made in preparing masters, it is of course necessary either to remove the ink or to render it non-transferable. The latter method is practically never used, since it is generally desired to replace the mistake rather than merely to erase it. Furthermore, covering the mistake produces an uneven surface for duplicating. Hence the art has long been concerned with the problem of removing a waxy mark containing dye from a coated paper base, without unduly disturbing the base.

One conventional method involves scraping with some sharp instrument such as a knife or razor lade or glass fibered brush. This produces messy particles containing dye, and unskillful operators will destroy the coated surface of the master, so that the correction will not type in properly.

An improvement on this method involves the use of a so-called correction pencil, which is a hard mixture of wax and clay in pencil form. It scrapes of the incorrect characters, producing debris, but the wax and clay tend to replace any coating that has been destroyed, so as to leave a surface which will accept the corrected imprint. However, this device still produces debris which tends to dirty anything with which it comes in contact.

I have discovered that it is possible selectively to re- 9 move the ink dyed wax characters from a hectographic master without the production of debris, by bringing into localized pressure contact with the selected characters a mass which under pressure is tackier than the dyed wax film, so that the ink will adhere to it, but which is insufiiciently tacky to disturb or rupture the surface of the master. Pressure is applied for only a short time, and

atent then removed; on lifting the mass, it takes the ink with it. No scraping or rubbing is involved.

The pressure-sensitive mass may be formed into a pencil, but preferably it is supplied in sheet form, coated onto some carrier such as paper. The pressure sensitive mass preferably carries some dye absorbent, such as clay, bentonite, carbon black, aluminum hydrate, etc.

The selection of the ingredients of the pressure sensitive mass depends on the nature of the ink to be removed, and the strength of the paper from which it is to be lifted; the stronger the paper, the tackier the composition can be. With the general run of commercial papers and inks, certain waxes are sufiiciently tacky in themselves, certain other waxes need to be tackified by additions of resin; and where the correction device is to be prepared in sheet form some waxes are sufficiently tacky, but require plasticizer to produce satisfactory adhesively coated sheets.

Beeswax, microcrystalline paraifin wax, Japan wax and most low melting petroleum pitches are sufficiently tacky to be used alone as the base of my new composition. Ordinary crystalline parafiin wax (150 F. M. P.), ceresine, Chinese insect wax, spermaceti, Halowax, (chlorinated paraifine) and Carbowax (polyethylene glycol) all require some resinous tackifying addition. Typical of tack-producing addants are rosin and its derivatives, cumarone-indene and other hydrocarbon resins, rubbery materials such as polyisobutylene, and chlorinated diphenyl. Certain waxes are too hard and brittle for the contemplated purpose, and need to be plasticized. Such waxes include, for example, candellila, esparto, ouri-curi, montan, sugar cane and Utah waxes. Carnauba wax is best used with both tackifier and plasticizer. Suitable plasticizers include, for example, petrolatum, mineral oil, lard oil, sperm oil, castor oil, lanolin and low melting (120 F.) paraffin wax. Even shellac softened with Venice turpentine can be used in appropriate circumstances.

As indicated above, I prefer to employ an absorbent to help remove the ink. In general, 10 to 20% of absorbent is desirable for optimum results.

As examples of my invention, masters were prepared from transfer sheets made in accordance with my Patent No. 2,671,734, using an ink of the following composihon:

Parts by weight Refined Carnauba wax 19.25 Sugar cane wax 24.75 Castor oil 19.25 Petrolatum 27.5. Mineral oil 100 27.5 Crystal Violet 156.75

These masters could be successfully corrected with adhesive masses of the following compositions, in either film or pencil form:

Patented May 27, 1958 It should be noted that these products are not pressure-sensitive adhesives in the ordinarysense; if applied to? asolidf surface, they will not adhere under. any pres- 7 sure which can be applied under ordinary circumstances. Rather, they are slightly tacky, in the sense that they will. adhere lightly and'imr'nediately, pull away. The impo'n tantpointis that they have slightly. more pull than the ink, but less than the surface. on which the inkis: resting.

'Thecomposition should' in all cases be compounded in such a way that a maximum amount, of tackiness is 'attained with due regard to therelatively small localized pressure tov be employed by the user, the nature of the};

dye or ink to be picked up, and the quality of thepaper.

rother material of the master sheet. The point. at which fibers of the master sheet begin'to be torn away is a measure. of the maximum adhesiye quality to be developed.

Whilethere is no really satisfactory standard method strengthjof paper-(i. e., the resistance to separation of coatings or fibers) can be conveniently alluded to in describing the tackiness to be employed in the practice of the present invention. Standard Test #T459 m-4 5) areg'used by applying melted masses to the surface of. the paper tobe tested, allowing them to cool then pulling them..o'ff. Measured in terms of these'kn'own wtest waxes, the ink compositions usually employed .in making master sheets have. a tackiness' of 2A to 3A, and the'new pressure-sensitive ink-removing wax compositions provided by this invention have a tacki; ness between 3A and 9.

. Wh'en used'as a coating .on paper, the correctionfilm applied may'vary in thickness, preferably being from .0001 to .0020 inch in thickness. 1 I

It will thus be observed that I am successfully achieving V the result "desired by recourse toja phenomenon which has usually heretofore been considered a nuisance, viz,

the transfer of ink from one surface to another by an act of offsetting. Forexample, when carbon papers, especially spirit carbons-are staekedsoithat the inked face The Dennison waxes (TAPPI.

for testing tackiness, or defining it in numerical terms, it 7 V a may be noted that the "wax sticks developed by Dennison Manufacturing Co. forjmeasuring the surface bonding is in contact-withthepaper backing-of'the adjacent sheet, 7

some ofv the ink'willundereer-tain'eonditi ons of pressure and temperaturetransfer tothe adjacent sheet and make it messyI- -I!1 accor-mdancewith-my invention, the correc- 5 tioncomposition is sodevised-as to encourage this transfer ofdye from the sheet-to be corrected to the-composi tion that is pressed against it. Essentially, the composi 7 tion is of an adhesive nature, i. e., adhesive to the inkto be lifted when a mild localized pressure is exerted; and the desired result can be attained without inclusion of an absorbent in the composition, -although theadclition of an absorbentingredient is generallyto beipreferredn The adhesive and absorbent nature of the presentj composition distinguishes it.from; the conventional, correctionpenc' whose primary ability-must be its-ink 'scrapingqualit-y, and.

whose friability must be such as to produce scrapings that can be readily brushed or blown away. It is just such scraping andbrushing that nay-invention is aimed to avoid. At thelsame'time, it'shouldfbe noted that the removal of ink by the present composition is not dependent upon any softening of the w'axyfmass. In fact, any appreciable softening or spreading underispressure is'undesirable if clean-cut accurate corrections are? to result. 7

It will beunderstood that the details and'proport-ions herein specificedarei in many respects set forth merely byway of example, and thatchangesf maybe made by those skilled in the art without necessarily departing from the spirit and scope of the invention'as 'expressed in'the' appendedclaimsl I Havingthus described my invention what Iclaim as" new and desire to secure by Letters Patent-is; i

l. A correction sheet for the-removal, without rubbing or abrasion, of an unwanted spirit duplicating ink mark" from a hectographic'maste r' sheet composed'essentially ofpaper, comprising a backing sheet coated' with-a film; of material which is only slightly tacky'under moderatepressure, said material being more tacky than-conventional spirit duplicating inks whereby it will' remove ink from said unwanted ink mark when firmly pressed againstit, but' insufiicientlytacky to pick fiber fromthe paper of y 7 which the-master'sheetis composed; said material comprising' a major portion of wax and 10 to 20% of 8",.

filler which is an absorbent for spirit duplicating inks,

2. A correction sheet as definedin claim 1", 'inwhich; the wax is predominantly microcrystalline paraffin wax;

' 3. A correction sheet as defined in claim 1, in' which 7 the filler is selected from the group of dye absorbe'nts consisting of clay, bentonite, carbon black and aluminum hydrate. 1

References Cited in the tile of this patent UNITED STATES PATENTS 1,415,293 Baldwin May 9,1922," 1,714,702 Van Arsdel May28, 1929, 1,813,675 Moore L Julyg7,19 31= 7 1,995,685 Perkins Mar. 26,1935,

' 2,142,761 Jan. 3,,1939 2,164,035 Jones June 27,, 1 939.

Baldwin V Y Dec 13,1221;

Larsen Man 6,19,56 

1. A CORRECTION SHEET FOR THE REMOVAL, WITHOUT RUBBING OR ABRASION, OF AN UNWANTED SPIRIT DUPLICATING INK MARK OF PAPER, COMPRISING A BACKING SHEET COATED WITH A FILM OF PAPER, COMPRISING A BACKING SHEET COATED WITH A FILM OF MATERIAL WHICH IS ONLY SLIGHTLY TACKY THAN CONVENPRESSURE, SAID MATERIAL BEING MORE TCKY THAN CONVENTIONAL SPIRIT DUPLICATING INKS WHEREBY IT WILL REMOVE INK FROM SAID UNWANTED INK MARK WHEN FIRMLY PRESSED AGAINST IT, BUT INSUFFICIENTLY TACKY TO PICK FIBER FROM THE PAPER OF WHICH THE MASTER SHEET IS COMPOSED, SAID MATERIAL COMPRISING A MAJOR PORTION OF WAX AND 10% TO 20% OF A FILLER WHICH IS AN ABSORBENT FOR SPIRIT DUPLICATING INKS. 